Android E-commerce App Development

I'm looking to develop an Android e-commerce app with the following core features:

- User Login/Registration
- Product Catalog
- Payment Gateway Integration
- Location Services

Ideal skills and experience:
- Proven experience in Android app development
- Strong background in developing e-commerce platforms
- Expertise in integrating secure payment gateways
- Familiarity with location services and geolocation features
- UI/UX design skills for a user-friendly experience

Please provide a portfolio of similar projects and an estimated timeline.